The present invention is directed to the field of motorcycles. More specifically, the present invention is directed to a neutral starter interlock, a form of electronic safety circuit, that may be retrofit to Harley-Davidson® Big Twin (encompassing models in the Touring, FXR/Dyna,™ and Softail® families) and Sportster® motorcycles manufactured prior to model-year 2007 and factory equipped with an electric starter and a neutral indicator light. The starter motor on these motorcycles will turn over with the transmission either in neutral or in gear. Starting is uneventful if the transmission is in neutral. With the transmission in gear, however, hitting the electric-starter button causes the motorcycle to lurch forward unless or until the clutch is disengaged. Even if the clutch lever is pulled in before hitting the starter button with the transmission in gear, the motorcycle will typically rock ahead until the clutch plates fully release. The motorcycle lurching forward unexpectedly can result in physical injury to the rider, to a passenger, or to a bystander and/or in damage to the motorcycle or to a nearby vehicle. Hence, a representative Owner's Manual warns: “Before starting engine, always shift transmission to neutral to prevent accidental movement which could result in death or serious injury” (2002 Harley-Davidson® Owner's Manual, Touring Models, p. 162).
With the addition of the present invention, the starter motor on one of these motorcycles will turn over and the engine start only when the transmission is in neutral. Hitting the starter button when the transmission is in gear, even with the clutch lever pulled in, results in no action, rather than in forward movement of the motorcycle, as is currently the case.
In apparent recognition of the safety concerns imposed by its traditional starting system, Harley-Davidson Motor Company® has equipped all its model-year 2007 motorcycles with a starter interlock (referred to as a clutch/neutral interlock) that performs a function similar to that of the present invention. Harley-Davidson's stock system for 2007 models (which includes a provision for starting the motorcycle with the transmission in gear if the clutch lever has been pulled in), however, is not designed as a retrofit for earlier models.
The present invention, in the most general terms, represents an improvement in a motorcycle having an engine, a transmission, a transmission neutral switch, an electric starter motor, a starter solenoid for energizing the starter motor, a battery, and electronic circuitry that includes a neutral indicator circuit interconnected between the battery and the transmission neutral switch for illuminating an indicator light whenever the transmission is in neutral and a starting circuit interconnected between the battery and the starter solenoid, activated via an ignition switch and electric-starter button, for enabling the starter motor to initiate engagement of the engine; the improvement comprising an interlock circuit capable of being retrofit within the motorcycle's existing electronic circuitry so as to interconnect the neutral indicator circuit and the starting circuit to prevent the starter motor from initiating engagement of the engine when the transmission is in gear. This interlock circuit comprises an electronic relay interposed within the starting circuit, the relay having a switch side that creates an open circuit between the battery and the starter solenoid when the transmission is in gear, even with the starting circuit otherwise activated. The electronic relay further comprises a coil side connected to the neutral indicator circuit, this connection providing a conduit to ground for the coil side through the closed neutral switch when the transmission is in neutral, thereby closing the switch side of the relay and allowing current to flow from the battery to the starter solenoid when the starting circuit is activated.
Various other features, advantages, and characteristics of the present invention will become apparent after a reading of the following detailed description.